Waters of the United States

For purposes of the Clean Water Act, "Waters of the
United States" means:

(a) All waters which are currently used, were used in the
past, or may be susceptible to use in interstate or foreign commerce,
including all waters which are subject to the ebb and flow of the tide;

(b) All interstate waters, including interstate "wetlands";

(c) All other waters such as interstate lakes, rivers, streams
(including intermittent streams), mudflats, sandflats, wetlands, sloughs,
prairie potholes, wet meadows, playa lakes, or natural ponds the use,
degradation, or destruction of which would affect or could affect interstate
or foreign commerce including any such waters:

(1) Which are or could be used by interstate or foreign
travelers for recreational or other purposes;

(2) From which fish or shellfish are or could be taken
and sold in interstate or foreign commerce; or

(3) Which are used or could be used for industrial purposes
by industries in interstate commerce;

(d) All impoundments of waters otherwise defined as waters
of the United States under this definition;

(e) Tributaries of waters identified in paragraphs (a) through
(d) of this definition;

(f) The territorial sea; and

(g) Wetlands adjacent to waters (other than waters that
are themselves wetlands) identified in paragraphs (a) through (f) of this
definition.

Waste treatment systems, including treatment ponds or lagoons
designed to meet the requirements of CWA are not waters of the United
States.

NB: The Judicial Branch has made several rulings further clarifying this definition, of which are not included in this regulatory citation.